JP2689855B2 - Air pressure setting method and device for die cushion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die cushion device of a press machine, and more particularly to a method and device for setting an air pressure of an air cylinder for urging a cushion pad upward.

[0002]

2. Description of the Related Art Press machines for drawing are generally
(A) a cushion pad supporting a wrinkle holding die,
(B) An air cylinder for urging the cushion pad upward, and a die cushion device for applying a wrinkle pressing load based on the air pressure of the air cylinder. The press machine described in Japanese Utility Model Laid-Open No. Sho 62-20711 is an example, and the air pressure is set so that a trial press is performed every time the mold is replaced so that a proper press product can be obtained by trial and error. It is usually adjusted.

However, when the air pressure is adjusted by trial and error as described above, not only is it troublesome and time-consuming, but also it requires skill to work and it is difficult to stably obtain a pressed product of a certain quality. . Therefore, the applicant of the present application, in Japanese Patent Application No. 4-114004, applied the air pressure to obtain an appropriate pressed product based on the mold information specific to the mold and the machine information specific to the press machine. A method of automatic setting was proposed. For example, the press machine shown in FIG. 1 will be specifically described. A target wrinkle pressing load Fso capable of performing appropriate drawing processing, a weight Wr of a wrinkle pressing ring (wrinkle pressing type) 28, a cushion pin 2
The number n of the two used is previously obtained for each mold by a tri-press (press machine that performs trial punching at the time of manufacturing the mold) or the like, and the weight Wa of the cushion pad 26, the weight Wp of the cushion pin 22 and the air cylinder 32 are determined. Using the pressure receiving area A, the air pressure Pax is calculated according to the following equation (1) so that the air pressure Pa in the air tank 34 becomes the air pressure Pax.
The air pressure sensor 39 controls the switching of the air pressure control circuit 38 and the open / close valve 37 while detecting the air pressure Pa.

[Formula 1] Pax = (Fso + Wa + Wr + n · Wp) / A (1)

[0004]

By the way, the supply of the pressure air to the air cylinder reduces the time for changing the mold including the setting of the air pressure. For example, when the mold is changed, the upper press die is attached to the press slide. For example, when the cushion pad was held at the lower end, the air pressure was also adjusted. However, if the cushion pad is subsequently raised, the air pressure will decrease as the volume of the air cylinder increases, so it is necessary to supply pressurized air again after the cushion pad has risen, and press work is started by that amount. There was a problem that the time until was delayed.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide an air pressure so that an appropriate wrinkle holding load can be obtained during press working with the cushion pad held at the lower end. The purpose is to adjust the cylinder air pressure and shorten the mold replacement time.

[0006]

In order to achieve such an object, the air pressure should be adjusted in consideration of the volume change of the air cylinder due to the rise of the cushion pad. ) A die for a press machine that includes a cushion pad supporting a wrinkle holding die and (b) an air cylinder that biases the cushion pad upward, and applies a wrinkle holding load based on the air pressure of the air cylinder. In the cushion device, a method of setting the air pressure so as to obtain a predetermined target wrinkle pressing load during press working, comprising: (c) holding the cushion pad at an initial position lower than during press working. In this state, the initial air pressure at which the target wrinkle pressing load is obtained during press working regardless of the volume change of the air cylinder is The initial air pressure calculation step of calculating based on the mold information about the wrinkle presser die and the machine information about the die cushion device, and (d) the air pressure in the state where the cushion pad is held at the initial position. An air pressure adjusting step of adjusting the air pressure of the cylinder to the initial air pressure.

[0007]

According to such an air pressure setting method, in the state where the cushion pad is held at the initial position, the initial air pressure at which the target wrinkle pressing load is obtained during the press working is set to the mold. In addition to the calculation based on the machine information and the machine information, the air pressure of the air cylinder is adjusted to its initial air pressure. Pressing is performed while holding down. Therefore, for example, when attaching the upper press die to the press slide when exchanging the mold, pressure air is supplied to the air cylinder with the cushion pad held at the initial position, and the air pressure is adjusted to the above initial air pressure. If so, the air pressure does not need to be readjusted after the cushion pad rises, and the time until the start of press working is shortened by that much, and the operating rate of the press machine is improved.

Here, as the die information and machine information, the target wrinkle holding load Fso and the wrinkle holding die weight W are given.
r, the weight Wa of the cushion pad, the pressure receiving area A of the air cylinder, and the like, information about the volume change of the air cylinder between when the cushion pad is held at the initial position and during press working, for example, the cushion stroke during press working. And air pad dimensions at the cushion pad initial position,
The size of the air chamber at the rising end of the cushion pad and the volume of the air tank communicating with the air cylinder are required.

[0009]

In order to achieve the above-mentioned object, a second invention is (a) a cushion pad supporting a wrinkle holding die, and (b) attaching the cushion pad upward. In a die cushion device of a press machine that is provided with an urging air cylinder and applies a crease presser load based on the air pressure of the air cylinder, the air pressure is adjusted so that a predetermined target crease presser load is obtained during press working. (C) The target wrinkle pressing load is obtained at the time of press working regardless of the volume change of the air cylinder in a state where (c) the cushion pad is held at an initial position lower than that at the time of press working. Input means for inputting mold information relating to the wrinkle pressing die, including the target wrinkle pressing load, which is necessary for calculating the initial air pressure to be applied, and (d) the initial Machine information storage means for storing machine information about the die cushion device necessary for calculating the pressure, and (e) initial air for calculating the initial air pressure based on the mold information and the machine information. Pressure calculating means, and (f) air pressure adjusting means for adjusting the air pressure of the air cylinder to the initial air pressure calculated by the initial air pressure calculating means while the cushion pad is held at the initial position. And having.

[0010]

That is, the second aspect of the present invention relates to an air pressure setting device for automatically setting the air pressure according to the air pressure setting method of the first aspect of the present invention. Based on the machine information stored in the machine information storage means, the initial air pressure calculation means calculates the initial air pressure, and when the cushion pad is held at the initial position, the air pressure of the air cylinder is changed to the initial air pressure. The pressure is automatically adjusted by the air pressure adjusting means. In this case, since the air pressure of the air cylinder is automatically set, in addition to the effect of the first aspect of the invention, the burden on the operator is reduced, and the air pressure is erroneously set due to an operation error or the like. Avoided.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an example of a press machine for drawing an outer panel of an automobile. A bolster 12 to which a punch die 10 is attached is arranged on a base 16 via a press carrier 14, while a die die 18 is installed. The press slide 20 to be attached is vertically driven by a drive mechanism (not shown). In the bolster 12,
A large number of through holes 24 are provided to dispose the cushion pins 22.
A cushion pad 26 for supporting the cushion pins 22 is provided below the bolster 12. The cushion pin 22 supports the wrinkle pressing ring 28 that is arranged together with the punch die 10, and is arranged in an arbitrary number at a predetermined position that is predetermined according to the shape of the wrinkle pressing ring 28. . The cushion pad 26 includes a number of hydraulic cylinders 30 corresponding to the through holes 24, and the lower ends of the cushion pins 22 are respectively brought into contact with the piston rods of the hydraulic cylinder 30. The wrinkle retainer ring 28 corresponds to a wrinkle retainer type.

The cushion pad 26 is arranged in the press carrier 14 so as to be movable in the vertical direction, and is always urged upward by the air cylinder 32. The air chamber 33 of the air cylinder 32 is communicated with an air tank 34, and the air tank 34 is supplied with pressurized air from an air pressure source 36 via an air pressure control circuit 38. An open / close valve 37 and an air pressure sensor 39 are connected to the air tank 34. The air pressure control circuit 38 and the open / close valve 37 adjust the air pressure Pa in the air tank 34 and the air chamber 33 according to the wrinkle pressing load. Is pressed. That is, when the die die 18 is lowered together with the press slide 20, the peripheral edge portion of the work 40 is pinched between the die die 18 and the wrinkle holding ring 28, and the die die 18 and the punch die 10 are separated from each other. When the air cylinder 32 is pushed down through the wrinkle holding ring 28, the cushion pin 22, the hydraulic cylinder 30, and the cushion pad 26 when the drawing process is performed with the wrinkle holding load, the wrinkle holding load corresponding to the air pressure Pa is wrinkled and held. It acts on the ring 28. A plurality of the air cylinders 32 are provided as needed, and the air chambers 33 of these air cylinders 32 are connected to a common air tank 34.

Further, the hydraulic chambers of the plurality of hydraulic cylinders 30 are communicated with each other through a pipe 46, and the pipe 46 is connected to a pipe 50 through a flexible tube 48, and an air-driven hydraulic pump. The hydraulic oil pumped up from the tank 54 by 52 is supplied through the check valve 56. A hydraulic control circuit 58 having a relief valve or the like is connected to the pipe 50,
The hydraulic control circuit 58 and the hydraulic pump 52 regulate the hydraulic pressure Ps of the hydraulic oil in the pipe 50 and the hydraulic cylinder 30. This oil pressure Ps is detected by an oil pressure sensor 60 connected to the pipe 46, and the wrinkle pressing load is evenly transmitted via the plurality of cushion pins 22, in other words, all the oil pressures during press working. The piston of the cylinder 30 is adjusted to be in a neutral state.

In this embodiment, a die cushion device 42 is constructed by including the air cylinder 32, the cushion pad 26, the hydraulic cylinder 30, and the cushion pin 22. Then, the air pressure P of the die cushion device 42.
a and the hydraulic pressure Ps are controlled by the control unit 62 shown in FIG.
Signals representing the air pressure Pa and the oil pressure Ps are supplied from the air pressure sensor 39 and the oil pressure sensor 60 via an amplifier and an A / D converter. The control unit 62 includes a CPU, RAM, R
A microcomputer including an OM or the like is included, and by performing signal processing in accordance with a program stored in advance in the ROM, the opening / closing valve 37, the air pressure control circuit 38, and the hydraulic control circuit 58 are switched, or the hydraulic pump. The air pressure Pa and the hydraulic pressure Ps are adjusted by operating 52. The control unit 62 is also connected to the display / operation panel 64 shown in FIGS. 3 to 5, and the display / operation panel 64 is provided with various operation switches and indicators.

Further, the control unit 62 is
A machine information memory 66 and a mold information memory 68 are provided. Machine information unique to the press machine is stored in advance in the machine information memory 66 with a keyboard, a personal computer, etc., and the mold information memory 68 transmits and receives. Machine 70
ID card 7 attached to the punch die 10 by
Mold information peculiar to the mold read from No. 2 (see FIG. 1) is stored. As shown in FIG. 6, the ID card 72 includes a mold information memory 74 for storing mold information, a transmission / reception control CPU.
76, a transceiver 78, a battery, etc., and is configured to transmit the mold information stored in the mold information memory 74 by receiving the data acquisition signal transmitted from the transceiver 70. It has become.

The machine information and die information are information necessary for determining the air pressure Pa or the like at which proper press working can be performed, and are, for example, as follows. It should be noted that the mold information also includes information on the type of mold, that is, the model and number of the pressed product, the press machine used, the process, and the like. (Machine information) volume Va (mold cushion pressure receiving area A · initial air chamber dimension X of weight Wp-air cylinder 32 of the weight Wa-cushion pins 22 of the pad 26 _0-rising edge air chamber dimensions X _1, air tank 34 Information) ・ Weight Wr of presser foot presser ring 28 ・ Target presser foot presser load Fso ・ Number of cushion pins 22 used n ・ Cushion stroke L

Here, the weight Wa and the pressure receiving area A of the cushion pad 26 may be design values or actual measurement values, but for example, Japanese Patent Application No. 4-114 previously filed by the present applicant.
Using a load measuring device described in No. 007,
It is desirable to obtain a substantial value in consideration of sliding resistance and the like. When a plurality of air cylinders 32 are provided, the pressure receiving area A is the sum of the pressure receiving areas of all the air cylinders 32. The weight Wp of the cushion pin 22 is an average weight of a large number of cushion pins 22 used in the press machine, the weight Wr of the wrinkle holding ring 28 is an actually measured value, and the target wrinkle holding load Fso is, for example, the applicant first. Japanese Patent Application No. 4-
As described in No. 322405, while performing load measurement with a strain sensor attached to a plunger for vertically moving the press slide 20 or a frame of a press machine,
The condition of the wrinkle holding load for obtaining an appropriate pressed product is obtained by trial and error in advance. The load during the press working changes according to the press stroke, for example, as shown in FIG. 7, and the wrinkle holding load Fs between the die die 18 and the wrinkle holding ring 28 becomes closer to the bottom dead center, that is, the air cylinder 32. Although the target wrinkle pressing load Fso increases as the volume of the air chamber 33 decreases, the target wrinkle pressing load Fso is determined based on the wrinkle pressing load Fs at approximately the bottom dead center. Load F in Figure 7
f is a forming load between the punch die 10 and the die die 18. The number n of cushion pins 22 to be used is determined so that an appropriate pressed product can be obtained according to the shape of the wrinkle pressing ring 28 and the like.
Is a descending stroke of the cushion pad 26 accompanying the press working.

On the other hand, the initial air chamber size X ₀ is determined by the air chamber 33.
When the cushion pad 26 is moved to the rising end by the air cylinder 32, the rising end air chamber size X ₁ is the vertical dimension of the air chamber 33 in the state where the air inside is evacuated and the cushion pad 26 is locked at the lower end, that is, at the initial position. The volume Va of the air tank 34 is the total volume (excluding the air chamber 33) including the air tank 34 and the pipes communicating with the air tank 34 in the vertical dimension of the air chamber 33 (see FIG. 1) when the air chamber 33 is driven. These values may be designed values or actually measured values, but it is desirable to experimentally obtain them as follows. That is, the total air volume when the cushion pad 26 is held at the initial position is V ₀ , the air pressure (initial air pressure) Pa at that time is P ₀ , and the cushion pad 26 is pressed by the cushion stroke L from the rising end during press working. When the total air volume is V _L and the air pressure Pa is P _L at the time of lowering, that is, at the bottom dead center of the press, V ₀ =
_{Va + AX 0, V L =} Va + A (X 1 -L), P 0 V 0
= P _{L VL} , the following equation (2) is established, and the air pressures P ₀ and P _L can be measured by the air pressure sensor 39, and
Since the pressure receiving area A and the cushion stroke L are known, three different values are set as the initial air pressure P ₀ ,
If the air pressure P _L is measured, three unknowns X ₀ ,
X ₁ and Va are uniquely obtained. Any mold can be used in this case as long as the cushion stroke L is known, and a load measuring table or the like can be used instead of the mold. Further, X ₀ , X ₁ , and Va can also be obtained in one cycle of press operation by operating the press machine in an inching manner and measuring press strokes and air pressure Pa at three different locations. Further, the total air volume V ₁ = Va + AX ₁ when the cushion pad 26 is located at the rising end, and the air pressure P ₁ at that time
And the total air volume V ₀ and the initial air pressure P ₀ when the cushion pad 26 is held at the initial position, the following equation (3) is established. It is also possible to obtain X ₀ , X ₁ and Va in the same manner as above.

## EQU2 ## P ₀ / P _L = V _L / V ₀ = {Va + A (X ₁ -L)} / (Va + AX ₀ ) (2) P ₀ / P ₁ = V ₁ / V ₀ = (Va + AX ₁ ) / (Va + AX ₀ ) ... (3)

Next, a method of setting the air pressure Pa at the time of die replacement will be described with reference to the flowchart of FIG. The air pressure Pa is set such that the punch die 10 is fixed and the wrinkle pressing ring 2 is placed on the punch die 10.
The bolster 12 on which the die 8 and the die die 18 are placed is moved into the frame of the press machine and positioned at a predetermined die placement position.
Is performed in parallel with the work of attaching the press pad 20 to the press slide 20, and at this time, the cushion pad 26 is
2 is held at the initial position of the deflated lower end and is locked at the lower end by a hydraulic brake (not shown).

In step S1 of FIG. 8, the ID communication switch 80 of the display / operation panel 64 is operated to the "ON" side, and the read push button 82 is pressed, whereby the ID card 72 is pressed. The mold information is read and stored in the mold information memory 68, and the display / operation panel 64 is also included.
It is displayed on the ID data display section 84 of. The display 86 of the ID data display unit 84 displays the target wrinkle presser load Fso, the display 88 displays the weight Wr of the wrinkle presser ring 28, and the display 90 displays the number n of the cushion pins 22 used. The display 92 is for displaying the cushion stroke L. In the next step S2, the initial air pressure P ₀ is calculated according to the following equation (4) based on the machine information stored in the machine information memory 66 and the mold information, and in step S3, the air pressure Pa is calculated.
The air pressure sensor 39 controls the air pressure control circuit 38 and the open / close valve 37 so that the initial air pressure P ₀ becomes the initial air pressure P ₀ .

Equation 3] _{P 0 = Pax · {Va +} A (X 1 -L)} / (Va + AX 0) = (Fso + Wa + Wr + n · Wp) / A × {Va + A (X 1 -L)} / (Va + AX 0) ··· ( 4)

The above equation (4) is an arithmetic expression for calculating the initial air pressure P ₀ which gives the target wrinkle holding load Fso during press working regardless of the volume change of the air cylinder 32. The air pressure P _L at the dead point is (1) above.
This is a modification in which the air pressure P _{L in the} equation (2) is replaced with Pax so that the air pressure Pax is obtained according to the equation. As a result, when the cushion pad 26 is unlocked and lifted to perform press working, the air pressure P _{L at} the press bottom dead center becomes the air pressure Pax calculated according to the equation (1), and the target wrinkle pressing load Fso The wrinkle presser is performed. The weight Wr of the wrinkle holding ring 28 is generally less than 10 tons in the press working of the outer panel of the automobile, which is smaller than other members, and the air pressure Pa may be adjusted by ignoring this.

The ID data display section 84 of the display / operation panel 64 is provided with digital switches 94, 96, 98, 100 under the respective display units 86, 88, 90, 92, respectively. The display value can be changed accordingly, and if the ID communication switch 80 is turned on and the write push button 102 is pressed,
The stored contents of the ID card 72 are rewritten. In the case of a tri-press in which trial striking is performed at the time of manufacturing a die, the target wrinkle presser load Fso, the weight Wr of the wrinkle presser ring 28, the number n of the cushion pins 22 used, and the cushion stroke L are set to digital switches 94, 96, 98, 100. Set with, ID
By operating the communication switch 80 and the writing push button 102, the set value can be stored in the ID card 72.

Here, in the die cushion device 42 of the present embodiment, the target wrinkle holding load Fso during press working is performed with the cushion pad 26 held at the initial position.
The initial air pressure P ₀ is obtained according to the equation (4), and the air pressure Pa is adjusted to the initial air pressure P _0. Therefore, the pressure air is supplied after the cushion pad 26 is raised. There is no need to readjust the air pressure Pa, and the time until the start of press working is shortened by that much, and the operating rate of the press machine is improved. Further, since the calculation of the initial air pressure P ₀ and the adjustment of the air pressure Pa are automatically performed by the control unit 62, the burden on the operator is reduced, and the air pressure Pa is erroneously set due to an operation error or the like. Avoided.

In this embodiment, step S2 of FIG. 8 is the initial air pressure calculation step, and step S3 is the air pressure adjustment step. Further, the transceiver 70 and the ID card 72 correspond to input means for inputting mold information, the machine information memory 66 of the control unit 62 corresponds to machine information storage means, and of the series of signal processing by the control unit 62, The part that executes step S2 corresponds to the initial air pressure calculating means, and the part that executes step S3 constitutes the air pressure adjusting means together with the opening / closing valve 37, the air pressure control circuit 38, and the air pressure sensor 39.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, although the target wrinkle presser load Fso at the bottom dead center of the press is set in the above embodiment, the initial wrinkle presser load at which the cushion pad 26 is located at the rising end is the target wrinkle presser load Fso. It can also be set. In that case, the air pressure P ₁ when the cushion pad 26 is moved to the rising end may be set to the air pressure Pax obtained by the equation (1), and the information regarding the cushion stroke L is unnecessary. As well as
Since the initial air pressure P ₀ is calculated according to the following equation (5),
If the volume ratio (V ₁ / V ₀ ) is stored as machine information, the information on the capacity Va, the initial air chamber size X ₀ , and the rising end air chamber size X ₁ is not necessarily required. V ₁ / V ₀ =
Since it is P ₀ / P ₁ , the volume ratio (V ₁ / V ₀ ) can be easily obtained.

[Formula 4] P ₀ = Pax · (V ₁ / V ₀ ) ... (5)

Further, in the above-mentioned embodiment, the air pressure Pa is automatically adjusted by the control unit 62, but by the indicator for displaying the initial air pressure P ₀ calculated in step S2 and the air pressure sensor 39. An indicator for displaying the detected actual air pressure Pa, an operation switch for switching the on-off valve 37, and the air pressure control circuit 38 are provided on the display / operation panel 64 and the like so that the air pressure Pa can be adjusted by the operator's switch operation. You can The operator can also calculate the initial air pressure P ₀ .

In the above embodiment, the mold information was stored in the ID card 72 and read by the control unit 62 wirelessly. However, the mold information is recorded on a bar code, a magnetic tape, a floppy disk or the like. Then, the contents may be read by a reading device or the like connected to the control unit 62. It is also possible to manually input mold information using a keyboard or the like.

Further, in the above embodiment, the die cushion device 42 which supports the wrinkle pressing ring 28 through the large number of hydraulic cylinders 30 has been described. However, such a hydraulic cylinder 30 is not always necessary, and the cushion pin 26 is provided on the cushion pad 26. 22 may be directly contacted.

Although not specifically exemplified, the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a die cushion device that is an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a control system provided in the die cushion device of FIG.

FIG. 3 is a diagram showing the display / operation panel of FIG. 2 together with FIGS. 4 and 5;

FIG. 4 is a diagram showing a display / operation panel together with FIGS. 3 and 5;

5 is a diagram showing a display / operation panel together with FIGS. 3 and 4. FIG.

6 is a block diagram illustrating the function of the ID card attached to the punch type of FIG. 1. FIG.

FIG. 7 is a diagram illustrating a relationship between a load waveform of a press machine and a wrinkle holding load Fs.

8 is a flowchart illustrating an operation of adjusting the air pressure Pa of the die cushion device of FIG.

[Explanation of symbols]

26: Cushion pad 28: Wrinkle retainer ring (wrinkle retainer type) 32: Air cylinder 37: Open / close valve 38: Air pressure control circuit 39: Air pressure sensor 42: Die cushion device 62: Control unit 66: Machine information memory (machine information Storage means) 70: Transceiver (input means) 72: ID card (input means) Step S2: Initial air pressure calculation step (initial air pressure calculation means) Step S3: Air pressure adjustment step (air pressure adjustment means)

Claims (2)

(57) [Claims] 1. A press machine, comprising: a cushion pad supporting a wrinkle holding die; and an air cylinder for urging the cushion pad upward, and applying a wrinkle holding load based on the air pressure of the air cylinder. In the die cushion device, a method of setting the air pressure so as to obtain a predetermined target wrinkle pressing load at the time of press working, wherein the cushion pad is held at an initial position lower than that at the time of press working. In the above, in regard to an initial air pressure at which the target wrinkle pressing load is obtained at the time of press working regardless of the volume change of the air cylinder, die information about the wrinkle pressing die including the target wrinkle pressing load, and a machine related to the die cushion device. An initial air pressure calculation step that is calculated based on information, and the cushion pad is held at the initial position. State, the air pressure setting of the die cushion apparatus characterized by having an air pressure adjusting step of adjusting the air pressure of the air cylinder to the initial air pressure. 2. A press machine comprising a cushion pad supporting a wrinkle holding die and an air cylinder for urging the cushion pad upward, and applying a wrinkle holding load based on the air pressure of the air cylinder. In the die cushion device, a device for setting the air pressure so as to obtain a predetermined target wrinkle pressing load at the time of press working, wherein the cushion pad is held at an initial position lower than that at the time of press working. In, the die information regarding the wrinkle holding die including the target wrinkle holding load, which is necessary for calculating the initial air pressure for obtaining the target wrinkle holding load at the time of press working regardless of the volume change of the air cylinder, is input. Input means for operating the machine, and machine information storing machine information about the die cushion device necessary for calculating the initial air pressure. Storage means, initial air pressure calculation means for calculating the initial air pressure based on the mold information and the machine information, and an air pressure of the air cylinder in a state where the cushion pad is held at the initial position. And an air pressure adjusting means for adjusting to the initial air pressure calculated by the initial air pressure calculating means.